Slide surfacing for ski slopes



Dec. 15, 1970 J. w. G. WHITE E L 3,547,749

SLIDE SURFACING FOR SKI SLOPES Filed Jan. 31, 1969 iimmmsmm INVENTORS JAMES W. G. WHIITE HARRY A. FREEMAN ATTORNEYS United States Patent 3,547,749 SLIDE SURFACING FOR SKI SLOPES James W. G. White, Delavan, Wis., and Harry A. Freedman, Broomall, Pa., assignors to The Bnnker-Ramo Corporation, Oak Brook, Ill., a corporation of Delaware Filed Jan. 31, 1969, Ser. No. 795,667 Int. Cl. A63b 71/02; A63c 11/00; D036 27/00 US. Cl. 161-63 13 Claims ABSTRACT OF THE DISCLOSURE An all weather surfacing for ski slopes made up of joined together sections of sliver knit pile fabric back coated with a thick layer of resilient material. The pile is dense (1.5 to 3.5 pounds of available pile fiber per square yard) and high (0.5 to 2 inches). The individual pile fibers are thick (30 to 150 denier), and the upper onethird to one-quarter parts of the individual pile fibers are polished and given a directional lay so that, after installation of the surfacing on a slope, these end portions constitute the top face of the surfacing and extend down the slope. The pile may be uniform over the entire face of the fabric or it may be disrupted in accordance with patterns. All of the pile fibers may be the same length, or some may be longer than others.

BACKGROUND OF THE INVENTION This invention relates to a slide surfacing material for I ski slopes. The invention is concerned particularly with materials having characteristics such that skiers may descend slopes covered with the material in the same fashion and with much the same enjoyment as slopes covered with snow.

A number of attempts have been made heretofore to provide surfacing materials suitable for skiing. Such materials have been proposed for both indoor and outdoor installations with a view toward freeing the sport of skiing from its utter dependence upon the existence of a suitable covering of snow on an available slope.

However, in spite of the early recognition of the general desirability of such artificial skiing surfaces, the actual development of a truly satisfactory surfacing material has presented difficulties. Failures to simulate snow conditions in one way or another have been characteristic deficiencies of the various artificial skiing surface materials known heretofore. For example, it has been suggested that upstanding bristles be employed for this purpose, but the bristle materials did not simulate snow very closely with respect to potential skiing speed or ski turning characteristics. Moreover, skiers performing on such bristle covered surfaces were exposed to the risk of severe abrasion burns if they fell while moving at substantial speeds.

SUMMARY OF THE INVENTION The general object of the present invention is to obviate the deficiencies heretofore associated with artificial skiing surfaces and to provide a slide surfacing material which can be installed conveniently on a slope and which will coact with skis to give effects similar to those given by snow.

Other objects of the invention are to provide a slide surfacing material for ski slopes which is not apt to injure a falling skier by causing abrasion burns and to provide a resiliently deformable surfacing material of adequate lateral and longitudinal stiffness to bridge depressions in the ski slope and smooth out some of the bumps to be encountered by the skier.

These objects are accomplished, in accordance with the invention, through the provision of a sliver knit pile fabric having a dense, high pile made up of relatively large diameter synthetic staple fibers the upper end portions of which are bent over to extend generally parallel to and down the slope. These bent over fiber end portions present smooth surfaces for contacting the bottom faces of skis, and the friction forces tending to slow down the skiers are minimized. Good ski edge control is assured by the depth and resiliency of the pile. A skier can set his ski edges in the deep pile of the new surfacing material to control his movements in the same fashion as on snow.

The sliver knit pile fabric is back coated with a thick layer or layers of plastic or the like, flexible enough to permit the material to be installed. on slopes with ease but stiff enough to smooth out some of the bumps actually present on the slope. The back coating also contributes importantly to the tear strength characteristics of the slide surfacing material as a whole, permitting pieces of the material to be joined together by such mechanical means as industrial staples and enabling the material to Withstand the puncturing forces of ski poles.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of these and other aspects of the invention will be gained from a consideration of the following detailed description of certain embodiments illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic view showing a portion of a hill in vertical cross section and showing a slide surfacing in accordance with the invention disposed on the slope of the hill;

FIG. 2 is a diagrammatic vertical cross sectional view of a small segment of the slide surfacing extending down the slope of the hill;

FIG. 3 is a stylized reverse plan view illustrating the construction of the base of a pile fabric which forms a component of the slide surfacing material of FIGS. 1 and 2;

FIG. 4 is a diagrammatic cross sectional view depicting the orientation of the pile fibers of the fabric immediately after the knitting operation by which the pile fabric is formed but prior to the pile finishing operation which gives the upper end portions of the pile fibers the distinctive lay suggested in FIG. 2;

FIGS. 5 and 6 are schematic face views of other embodiments of the invention in which the pile face of the slide surfacing material is not uniform but is interrupted in accordance with patterns; and

FIG. 7 is a view similar to FIG. 2 but showing features of another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The FIG. 1 illustration of the slide surfacing material 2 of this invention as applied to a slope formed by a hill or mountain 4 is indicative of a presently preferred utilization of the invention. By covering its ski trails with the artificial skiing surface of the invention, a commercial ski resort may stabilize its season and free itself from complete dependence upon sometimes erratic weather conditions. If, at the beginning or end of a season, no snow at all is available, the surfacing material of the invention responds so well to the normal maneuvers of skiers that the skiers may pursue their sport without disappointment. Then, in mid-season when snow conditions are good, the presence of the slide surfacing material of the invention beneath the snow does not detract in any away from the enjoyment potential of the skiers.

The slide surfacing material 2 is made up of a sliver knit pile fabric 6 and a thick back coating 8, the characteristics of which will be referred to in greater detail below. The pile fabric 6 may be formed on conventional deep pile knitting machines of the type in which carding heads are provided for feeding pile forming staple fibers to knitting needles carried by a rotating needle cylinder. A suitable machine is disclosed, for example, in Brandt US. Pat. 2,710,525.

As shown in FIG. 3, the pile fabric 6 includes pile fibers 10 interlocked with a base 12 made up of knitted stitches of body or backin yarns 14. Although most of the pile fibers have been omitted from FIG. 3 so as not to confuse the illustration of the components, it will be understood that a great many pile fibers are interlocked with the knitted stitches and protrude from the face side of the backing 12. In this embodiment, the density of the pile is intended to be substantially uniform over the face of the fabric and all of the knitted stitches in the base 12 bear pile fibers 10.

The pile fibers 10 of the as-knit fabric 6 extend substantially vertically from the base or backing 12 as indicated in FIG. 4. Of course, the individual pile fibers have bends or crimps at various places along their lengths, but the general direction of the pile is a vertical one at this point in the manufacturing operation. In order to lock the pile firmly in place with respect to the knitted stitches of the backing 12, the backing is precoated with a suitable adhesive material, such as a filled acrylonitrile coating material.

The precoated fabric 6 is next subjected to the action of a machine generally known as an electrifier. Such a machine is shown, for example, in Schaab et al. US. Pat. 3,114,957. In this machine, the pile surface of the fabric 6 is pressed against a rapidly rotating heated roll which has a grooved surface. As the groove edges on the roller surface move along the upper end portions of the pile fibers 10-, these pile fiber portions are subjected to substantial heat, friction and pressure. Some of the crimp is removed from the pile fiber upper end portions and these portions are given a directional lay which disposes them generally parallel to the knitted backing 12. At the same time, the exposed fiber surfaces at the face of the pile fabric are smoothed and polished so as to minimize the drag which will be exerted by these fiber portions upon the base of a ski.

The orientation of the pile fibers 10 after the fabric has been subjected to the action of the electrifier machine is indicated in FIG. 2, where only a few of the pile fibers have been shown and where these have been greatly enlarged in size and stylized to emphasize certain significant characteristics. The bottom two-thirds to three-quarters parts of pile fibers 10 are fairly erect with respect to the base portion of the fabric, while the upper one-third to one-quarter parts of the pile fibers bend over to extend in the same general direction as the backing 12.

Ordinarily, the lower end portions of the pile fibers would not protrude from the base at angles of precisely 90 but would be inclined slightly in the direction of extent of the fiber upper end portions. Angles in the neighborhood of 80 are frequently encountered, for example. Substantial amounts of crimp are retained in these fiber lower end portions to assure that the pile will have the necessary resilience and bulk.

The fiber upper end portions overlie and are supported by the more erect portions of other pile fibers, so that fit the compression characteristics of the pile are basically those of a construction in which the fibers are loaded from their ends. During installation, the fabric is extended lengthwise down the slope 4 with the bent over pile fiber upper end portions directed downwardly. As a result, the skis rarely abut against fiber ends and the action of the skis in contacting the polished sides of fibers is not of a nature to generate high friction loads.

After the pile finishing operation carried out on the electrifier machine, the fabric 6 is provided with the back coating 8. Although various coating or laminating procedures may be employed if desired, a particularly convenient procedure is to pass the fabric 6 through a knife coater a plurality of times to apply sequentially a number of layers of the coating material to build up the desired thickness.

Various compositions may be employed for the back coating and the physical form of the material is not critical. In some instances, for example, foamed materials may be employed to advantage. The back coating selected should be resistant to weathering, flexible enough to provide for convenient installation, stiff enough to bridge some depressions in the slope and conform gently to the ground contours without disclosing small rocks or the like, strong enough to allow pieces of the material to be held together by industrial staples, and rupture resistant enough to withstand the puncturing forces of ski poles. For example, various vinyl resins such as polyvinylchloride meet these requirements.

The character of the pile of the fabric 6 will be affected by a number of factors such as pile density, pile height, and the nature and diameters of the pile fibers 10. Some ranges of suitable values for these variables will contribute to a more thorough understanding of the invention.

A convenient measure of pile density is the amount of fiber obtained by shearing the pile fiber off the finished fabric. In fabrics suitable for use in the present invention, the pile density may range from about 1.5 to about 3.5 pounds of available face fiber per square yard of fabric. The pile must be dense enough to prevent bottoming out of a ski during use but must not be so dense as to interfere with the setting of the ski edges into the pile for turning control and the like.

Suitable pile heights may fall within the range of from about 0.5 to about 2 inches. Pile height, like pile density, is important in preventing bottoming of the skis as well as in providing proper edge control. With pile heights substantially less than one-half inch, the probability of hottoming out becomes unacceptably high, and with pile heights substantially greater than 2 inches, there is a risk that the ski edges will catch in the deformed pile surface turning maneuvers or the like to upset the balance of the skier. Finished pile heights of from about 1 to about 1.5 inches ordinarily can be expected to give particularly good service.

The pile fibers used in the fabric of the invention should be relatively heavy staple fibers of synthetic materials. Fiber staple lengths in the range of from about 1.5 to about 4 inches are satisfactory. The materials employed should be ones which will not be adversely affected by exposure to ski slope conditions. Some examples are nylon, polyester, polypropylene, and acrylic fibers. Nylon 66 is particularly preferred because of its smoothness, weather resistance, toughness and resilience, and because fibers of this thermoplastic material can easily be polished and given the desired directional orientation by treatments on conventional electrifier machines.

Relatively thick fibers having deniers in the range of from about 30 to about 150 are suitable and fibers having deniers at least as great as 60 are especially preferred. These heavy fibers contribute a number of advantages. They retain their shapes and resiliency characteristics well and they are more durable than fine fibers in this environment where aggressive loading is commonplace. Additionally, these large diameter fibers minimize the ski-topile contact areas to hold down friction.

A specific example will serve to further illustrate the invention.

A deep pile fabric was knit on a sliver knitting machine supplied with Nylon 66 face or pile fibers and polyester backing yarns. The pile fibers were 60 denier and 2 inch staple length. The backing yarns were spun yarns designated 10/1 to indicate a size of 10 by the cotton count system and a singles construction. The knitted fabric was precoated to stabilize the structure with a filled acrylonitrile coating and was then subjected to the action of an electrifier machine the drum of which was heated to 400 F. The electrifier gave the fibers the distinctive orientation described above. The density of the pile was 2.25 pounds of available face fiber (that which is obtained by shearing the fiber off the finished fabric) per square yard. The backing yarn, buried face fiber and precoat weighed 1.75 pounds per square yard. The finished pile height was between 1 and 1.25 inches.

Then the fabric was passed over a knife coater a plurality of times to build up on the back thereof a back coating of 6 pounds per square yard of plasticized, pigmented and filled polyvinylchloride. This coating material weighed 10.4 pounds per gallon, had a hardness of 70 (Shore A), and had the following strength characteristics as measured by ASTM D-412: ultimate tensile strength, 1425 p.s.i.; stress required to elongate material 100%, 625 p.s.i.; elongation at break, 300%; and tear strength, 190 p.l.i.

Pieces of this slide surfacing were machine stapled together in place on a slope so as to cover an area to be traversed by skis. This installation gave excellent results. With no snow covering the installation, a skier could reach speeds comparable to those obtainable on snow, and the edge control characteristics of the surfacing were adequate for all the standard maneuvers.

Of course, other embodiments of the invention are entirely feasible. The invention can be applied to indoor installations as well as outdoor installations. Also, the new slide surfacing may be movably mounted and driven to pass upwardly beneath a skier in a space saving arrangement designed to provide sport or training in a small area. In some of these installations the back coating 8 may be reduced in size or otherwise altered to provide enhanced flexibility.

FIGS. through 7 suggest still other modifications.

Although a fabric having a uniform pile surface as described above may provide the desired skiing qualities in many instances. It may at times be preferable to reduce further the contact area between the skis and the pile. This may be accomplished by eliminating or shortening the pile in selected areas through knitting and/ or shearing techniques generally understood by producers of sliver knit fabrics. In the fabric 2a of FIG. 5, the pile 10a is omitted in rows v16 extending both longitudinally and transversely. In the fabric 212 of FIG. 6, the pile 10b is omitted according to a checkerboard pattern. Both embodiments yield a bumpy surface for contact with the bottoms of skis, thereby minimizing contact area and frictional drag. These configurations also make more pronounced the bite obtained during cornering and edging of the skis.

Another technique for improving the frictional properties of the surface without detracting from the bulk of the fabric is exemplified in the embodiment of FIG. 7. Here, the sliver knit pile fabric 6c is made up of a blend of long pile fibers 18 and short pile fibers 20. For example, the long fibers 18 might be about 3 inches long and the short fibers 20 might be about 2 inches long, and the blend might contain about percent of the long fibers 18 and percent of the short fibers 20.

When this fabric is subjected to the action of the electrifier machine as described above, the long fibers 18 react in substantially the same way as the fibers 10 of FIG. 2. That is, their upper end portions are straightened somewhat, polished and bent over approximately parallel to the backing. However, the shorter fibers 20 escape to a large extent the action of the grooved roller of the electrifier machine and these fibers remain in a generally upright condition throughout their lengths. The end result is that the ski contacting face of the material is constituted predominantly by the long fibers 18 which, in this case, are relatively few in number.

Additionally, it should be understood that not all the pile fibers in a given fabric need be of the same denier. Blends of fibers of different thicknesses (e.g., 60 and denier) may be used if desired, and in instances where fibers of different lengths are employed in combination, as in FIG. 7, it will sometimes be desirable to use long fibers of one denier and short fibers of another denier.

Still other modifications and variations will suggest themselves to persons skilled in the art. It is intended therefore that the foregoing description of certain embodiments be considered as exemplary only and that the scope of the invention be ascertained from the following claims.

Although the advantages of present invention have been described in connection with certain practical characteristic requirements for an artificial ski slope surface material, it should be understood that the inherent qualities of materials made in accordance with the present invention have utility in connection with the practice of other snow sporting activities such as, for example, sledding and tobogganing.

We claim:

1. An artificial skiing surface for a slope comprising a pile fabric including a base and pile fibers projecting upwardly from said base to form a dense pile of artificial fibers having deniers in the range of from about 30 of a height in the range of from about 0.5 inch to about 2 inches, the upper face of said pile being constituted by the upper end portions of said pile fibers being permanently bent and extending down said slope.

2. An. artificial skiing surface in accordance with claim 1, wherein said pile fibers are staple fibers having lengths in the range of from about 1.5 to about 4 inches, and wherein said bent over upper end portions of said pile fibers are polished and overlie upwardly extending portions of the pile fibers.

3. An artificial skiing surface in accordance with claim 1, wherein the density of said pile is in the range of from about 1.5 to about 3.5 pounds of available pile fiber per square yard of fabric.

4. An artificial skiing surface in. accordance with claim 3, wherein said pile is of substantially uniform density over the face of the fabric.

5. An artificial skiing surface in. accordance with claim 3, wherein said pile is interrupted at portions of the face of the fabric in accordance with a pattern.

6. An artificial skiing surface in. accordance with claim 5, wherein said pattern is made up of ridges extending longitudinally and horizontally.

7. An artificial skiing surface in accordance with claim 1, wherein the pile is made up of a blend of long and short fibers in which the short fibers predominate as to quantity, and wherein the upper face of the pile is constituted predominately by bent over upper end portions of the long pile fibers.

8. An artificial skiing surface according to claim 7, wherein said long and short pile fibers are of different deniers.

9. A resiliently deformable slide surfacing material for ski slopes providing good edge control characteristics for the skier, said material comprising a sliver knit pile fabric and a thick resilient back-coating adhered to said fabric; said fabric including a backing of knitted stiches, and pile fibers of deniers in the range of from about 30 to about 150 interlocked with said stitches and projecting from the side of said backing opposite said back-coating to provide a resilient pile having a density in the range of from about 1.5 to about 3.5 pounds of available pile fiber per square yard of fabric and having a height about the backing in the range of from about 0.5 to about 2 inches; said pile fibers including upper end portions extending generally lengthwise of the fabric at the upper face of said surfacing material whereby said material offers low frictional resistance to movement of skis thereover in the direction of extent of said pile fiber end portions.

10. A resiliently deformable slide surfacing material according to claim 9, wherein said back coating has a. tear strength sufficient to Withstand the puncturing force of ski poles.

11. A resiliently deformable slide surfacing material according to claim 9, wherein said pile fibers are nylon.

12. A resiliently deformable slide surfacing material according to claim 9, wherein said pile fibers have deniers at least as great as 60.

13. A resiliently deformable slide surfacing material according to claim 12, wherein the pile density is at least 2 pounds of available face fiber per square yard and the pile height is at least one inch.

References Cited ROBERT F. BURNETT, Primary Examiner MARK A. LITMAN, Assistant Examiner US. Cl. X.R. 

